Carbon Dioxide Absorbers: An Engaging Experiment for the General Chemistry Laboratory

A simple and direct method for measuring the absorption of carbon dioxide by two different substances is described. Lithium hydroxide has been used for decades to remove the gas from enclosed living spaces, such as spacecraft and submarines. The ratio of the mass of carbon dioxide absorbed to the mass of lithium hydroxide used obtained from this static method compares favorably with results in the literature that use a more complex constant-flow method. The method also works well for ethanolamine, another commonly used carbon dioxide absorber. The experiment for the general chemistry laboratory serves both quantitative and qualitative learning goals. Students compare stoichiometric calculations that assume a complete reaction with their experimental results to motivate use of the latter in predicting the amount of lithium hydroxide required for space missions. They use the ideal gas law to determine the mass of carbon dioxide absorbed. Their data allow a comparison of the performance characteristics of the two absorbers on the basis of their absorption capacity and the reversibility of their reactions with carbon dioxide. Students can also enhance their knowledge of descriptive chemistry by connecting qualitative observations during the reactions with species in the chemical equations.